If you have a young child or have been around little children, you know one thing for certain: they're likely to put stuff in their mouth that shouldn't go there.
For infants this is a natural and convenient way of exploring the world. Toddlers and slightly older children are also prone to chew on things that make adults react with alarm. However, for many children between the ages of two and three, compulsively eating non-food items is an eating disorder known as pica.
The word pica is Latin for magpie, a bird that will eat just about anything. Like that ravenous bird, children with pica do more than occasionally eat things like chalk and dirt. They crave and regularly eat things such as paint chips, clay, cornstarch, coffee grounds, glue, hair, and other household items. Kids might think those things are tasty and adults might see little harm in snacking on the occasional piece of chalk, but doctors consider pica to be a serious eating disorder because it can lead to health problems such as lead poisoning.
Doctors don't know what causes pica. Some suspect that nutritional deficiencies play a role. For example, some children with pica have been found to lack iron. Once given iron supplements, their craving for non-foods stopped. On the other hand, eating things like dirt and clay can cause iron deficiency, rather than result from it.
In any case, the most important thing is being able recognize pica when it occurs. If your child keeps eating non-foods compulsively for a month or longer, then it's best to consult a doctor.